Amniocentesis

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

What is amniocentesis?

Amniocentesis is a procedure whereby a sample of fluid is removed from the amniotic sac for analysis. The amniotic sac is in the uterine cavity. The amniotic sac is the fluid-filled structure inside
a pregnant woman's uterus within which the baby lives. Fetal cells, proteins, and fetal urine freely move within this sac.

During amniocentesis, fluid is removed by placing a long needle through the abdominal wall into amniotic sac. Sometimes, the woman's skin is injected first with a local anesthetic, but this is not usually necessary. The amniocentesis needle is typically guided into the sac with the help of ultrasound imaging performed either prior to or during the procedure. Once the needle is in the sac, a syringe is used to withdraw the clear amber-colored amniotic fluid,
that resembles urine. The volume of fluid withdrawn depends upon the age of the fetus and the reason for the testing.

The fluid can then be sent for evaluation of fetal lung maturity, genetic evaluation, evidence of spina bifida (a birth defect in spinal cord development) or other neural-tube defects, the presence of infection, or chromosome analysis. Chromosomes are structures that contain all of the genetic information in our cells. The amniotic fluid contains numerous free-floating fetal cells that can be grown in a laboratory. When these cells multiply and reach a certain number, their chromosomes are extracted and analyzed. It takes about two weeks to perform chromosome analysis. The fluid also contains proteins, minerals and other compounds that can be tested, and these studies may take 1 to 7 days to perform. Data obtained from amniotic fluid can help women make informed decisions regarding their pregnancies and babies.

For most patients, amniocentesis is a fairly quick and comfortable procedure. Some women experience some uterine cramping or a feeling of faintness.